Dynamic resource allocation, scheduling and signaling for variable data rate service in lte

ABSTRACT

A method and apparatus are provided for dynamic resource allocation, scheduling and signaling for variable data real time services (RTS) in long term evolution (LTE) systems. Preferably, changes in data rate for uplink RTS traffic are reported to an evolved Node B (eNB) by a UE using layer 1, 2 or 3 signaling. The eNB dynamically allocates physical resources in response to a change in data rate by adding or removing radio blocks currently assigned to the data flow, and the eNB signals the new resource assignment to the UE. In an alternate embodiment, tables stored at the eNB and the UE describe mappings of RTS data rates to physical resources under certain channel conditions, such that the UE uses the table to locally assign physical resources according to changes in UL data rates. Additionally, a method and apparatus for high level configuration of RTS data flows is also presented.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/842,543, filed Aug. 21, 2007, which claims priority from U.S.Provisional Patent Application No. 60/839,110 filed on Aug. 21, 2006which are incorporated by reference as if fully set forth.

FIELD OF INVENTION

The present invention is related to wireless communication systems. Moreparticularly, the present invention is related to a method and apparatusfor dynamic resource allocation, scheduling and signaling for variabledata rate service in long term evolution (LTE) systems.

BACKGROUND

Wireless communication systems are well known in the art. Communicationsstandards are developed in order to provide global connectivity forwireless systems and to achieve performance goals in terms of, forexample, throughput, latency and coverage. One current standard inwidespread use, called Universal Mobile Telecommunications Systems(UMTS), was developed as part of Third Generation (3G) Radio Systems,and is maintained by the Third Generation Partnership Project (3GPP).

A typical UMTS system architecture in accordance with current 3GPPspecifications is depicted in FIG. 1. The UMTS network architectureincludes a Core Network (CN) interconnected with a UMTS TerrestrialRadio Access Network (UTRAN) via an Iu interface. The UTRAN isconfigured to provide wireless telecommunication services to usersthrough wireless transmit receive units (WTRUs), referred to as userequipments (UEs) in the 3GPP standard, via a Uu radio interface.

For example, a commonly employed air interface defined in the UMTSstandard is wideband code division multiple access (W-CDMA). The UTRANhas one or more radio network controllers (RNCs) and base stations,referred to as Node Bs by 3GPP, which collectively provide for thegeographic coverage for wireless communications with UEs. One or moreNode Bs are connected to each RNC via an Iub interface. RNCs within aUTRAN communicate via an Iur interface.

The Uu radio interface of a 3GPP system uses Transport Channels (TrCHs)for transfer of higher layer packet containing user data and signalingbetween UEs and Node Bs. In 3GPP communications, TrCH data is conveyedby one or more physical channels defined by mutually exclusive physicalradio resources, or shared physical radio resources in the case ofshared channels.

To improve reliability of data transmission, automatic repeat request(ARQ) or hybrid ARQ (HARQ) is implemented. HARQ and ARQ employ amechanism to send feedback to the original sender in the form of apositive acknowledgment (ACK) or a negative acknowledgement (NACK) thatrespectively indicate successful or unsuccessful receipt of a datapacket to a transmitter so that the transmitter may retransmit a failedpacket. HARQ also uses error correcting codes, such as turbo codes, foradded reliability.

Evolved universal terrestrial radio access (E-UTRA) and UTRAN long termevolution (LTE) are part of a current effort lead by 3GPP towardsachieving high data-rate, low-latency, packet-optimized system capacityand coverage in UMTS systems. In this regard, LTE is being designed withsignificant changes to existing 3GPP radio interface and radio networkarchitecture, requiring evolved Node Bs (eNBs), which are base stations(Node Bs) configured for LTE. For example, it has been proposed for LTEto replace code division multiple access (CDMA) channel access usedcurrently in UMTS, by orthogonal frequency division multiple access(OFDMA) and frequency division multiple access (FDMA) as air interfacetechnologies for downlink and uplink transmissions, respectively. LTE isbeing designed to use HARQ with one HARQ process assigned to each dataflow and include physical layer support for multiple-inputmultiple-output (MIMO).

LTE systems are also being designed to be entirely packet switched forboth voice and data traffic. This leads to many challenges in the designof LTE systems to support voice over internet protocol (VoIP) service,which is not supported in current UMTS systems. VoIP applicationsprovide continuous voice data traffic such that data rates vary overtime due to intermittent voice activity. Variable data rate applicationslike VoIP provide specific challenges for physical resource allocation,as described below.

eNBs in LTE are responsible for physical radio resource assignment forboth uplink (UL) communications from a UE to the eNB, and downlink (DL)communications from eNB to a UE. Radio resource allocation in LTEsystems involves the assignment of frequency-time (FT) resources in anUL or DL for a particular data flow. Specifically, according to currentLTE proposals, FT resources are allocated according to blocks offrequency subcarriers or subchannels in one or more timeslots, generallyreferred to as radio blocks. The amount of physical resources assignedto a data flow, for example a number of radio blocks, is typicallychosen to support the required data rate of the application or possiblyother quality of service (QoS) requirements such as priority.

It has been proposed that physical resource allocation for DL and ULcommunications over the E-UTRA air interface in LTE can be made validfor either a predetermined duration of time, known as non-persistentassignment, or an undetermined duration of time, known as persistentassignment. Since the assignment messages transmitted by the eNB maytarget both the intended recipient UE of the assignment as well as anyUEs currently assigned to the resources specified by the assignment, theeNB may multicast the assignment message, such that the control channelstructure allows for UEs to decode control channel messages targeted forother UEs.

For applications that require sporadic resources, such as hypertexttransport protocol (HTTP) web browser traffic, the physical resourcesare best utilized if they are assigned on an as-need basis. In thiscase, the resources are explicitly assigned and signaled by the layer 1(L1) control channel, where L1 includes the physical (PHY) layer. Forapplications requiring periodic or continuous allocation of resources,such as for VoIP, periodic or continuous signaling of assigned physicalresources may be avoided using persistent allocation. According topersistent allocation, radio resource assignments are valid as long asan explicit deallocation is not made. The objective of persistentscheduling is to reduce L1 and layer 2 (L2) control channel overhead,especially for VoIP traffic, where L2 includes the medium access control(MAC) layer. Persistent and non-persistent assignments by the L1 controlchannel may be supported using, for example, a persistent flag or amessage ID to distinguish between the two types of assignment in anassignment message transmitted by the eNB.

FIGS. 2 and 3 illustrate examples of persistent allocation offrequency-time resources in LTE, where each physical layer sub-framecomprises four time interlaces to support HARQ retransmissions ofnegatively acknowledged data. Each interlace is used for thetransmission of a particular higher layer data flow, such that the sameinterlace in a subsequent sub-frame is used for retransmission ofpackets that were unsuccessfully transmitted. A fixed set offrequency-time (FT) resources are assigned in each interlace for controltraffic as a control channel, which may include the L1 common controlchannel (CCCH) and synchronization channel.

FIG. 2 shows an example of persistent allocation and deallocation. Insub-frame 1, a first set of frequency-time resources (FT1), includingone or more radio blocks, are allocated to UE₁ via the control channel.Assuming the transmission of data to UE₁ completes after i−1 sub-frames,the eNB sends in sub-frame i a control message to UE₁ and UE₂ in orderto deallocate resources FT1 from UE₁ and allocate them to UE₂. Thecontrol channel can be used in the intermediate sub-frames betweensub-frames 1 and i for the assignment of other FT resources. FIG. 3shows an example of persistent allocation and expansion, where eNBassigns additional physical resources FT2 to UE₁ in sub-frame i tosupport additional traffic for UE₁.

A characteristic of many real time services (RTS), such as voiceservices, is variable data rates. In the case of voice services, aconversation is characterized by periods of speech followed by periodsof silence, thus requiring alternating, constantly varying data rates.For example, a typical adaptive multi-rate (AMR) channel for voiceservice supports eight encoding rates from 4.75 Kbps to 12.2 Kbps and atypical adaptive multi-rate wide-band (AMR-WB) channel supports nineencoding rates from 6.6 Kbps to 23.85 Kbps.

Current techniques for persistent resource scheduling are not designedto accommodate variations in data rates. Under conventional persistentallocation, physical resources are allocated to support either a maximumdata rate for a data flow or some sufficiently large fixed data ratesupported by the physical channel. Accordingly, physical resources arewasted because the resource allocation is not able to adapt to changesin required data rates resulting from, for example, intermittent voiceactivity.

In order to support variable data rates, an eNB must be signaled thechanging data rates for both UL and DL traffic. In LTE systems, an eNBcan easily monitor DL data rate variations that originate at the eNB andmake efficient DL resource assignment. However, current UMTS systems andproposals for LTE systems do not provide a manner for an eNB to monitordata rate variations for UL traffic originating at a UE so that the eNBmay accordingly assign the appropriate amount of UL physical resourcesin a dynamic and efficient manner. Additionally, current proposals forLTE systems do not support high-level configuration operations for VoIPservice.

The inventors have recognized that there is a need in LTE systems forsupport of dynamic resource allocation in combination with persistentresource allocation, along with efficient scheduling and controlsignaling, in order to support RTS applications with changing data ratessuch as VoIP. Therefore, the inventors have developed a method andapparatus for solving these problems in LTE systems.

SUMMARY

A method and apparatus for radio resource allocation, scheduling andsignaling for variable data rate and real time service (RTS)applications are provided, where the present invention is preferablyused in long term evolution (LTE) and high speed packet access (HSPA)systems.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the invention may be had from thefollowing description, given by way of example and to be understood inconjunction with the accompanying drawings wherein:

FIG. 1 is a block diagram of the system architecture of a conventionalUMTS network;

FIG. 2 is a diagram showing an example of persistent assignmentallocation and deallocation in the time-frequency domain;

FIG. 3 is a diagram showing an example of persistent assignmentallocation and expansion in the time-frequency domain;

FIG. 4 is a flow diagram of a method for high-level configuration ofreal time services (RTS), in accordance with a first embodiment of thepresent invention;

FIG. 5 is a flow diagram of a method for signaling variable data ratesfor uplink traffic, in accordance with a second embodiment of thepresent invention;

FIG. 6 is a flow diagram of a method for dynamic allocation andsignalling of radio resources at an evolved Node B (eNB) for RTS withvariable data rates, in accordance with a third embodiment of thepresent invention; and

FIG. 7 is a flow diagram of a method for dynamic allocation andsignalling of radio resources at a user equipment (UE) for RTS withvariable data rates, in accordance with a fourth embodiment of thepresent invention.

DETAILED DESCRIPTION

Hereafter, a wireless transmit/receive unit (WTRU) includes but is notlimited to a user equipment (UE), mobile station, fixed or mobilesubscriber unit, pager, or any other type of device capable of operatingin a wireless environment. When referred to hereafter, a base stationincludes but is not limited to a Node-B, evolved Node B (eNB), sitecontroller, access point or any other type of interfacing device in awireless environment. A base station is a type of WTRU.

Although Third Generation Partnership Project (3GPP) long term evolution(LTE) is used by way of example in the following description, thepresent invention is applicable to wireless communication systemsincluding, but not limited to, high speed packet access (HSPA) and HSPAevolution (HSPA+) systems. Additionally, real time services (RTS) suchas voice over internet protocol (VoIP) are used by way of example todescribe the invention. However, the present invention is intended tosupport any intermittently transmitting or variable data applications,and may also be used to adapt resource allocation for retransmissions.In the following, radio access bearer (RAB) or logical channel may beused interchangeably with data flow.

According to a first preferred embodiment, high-level information for aRTS data flow including a data flow identification (ID), or equivalentlya radio access bearer (RAB) or logical channel ID, and a hybridautomatic repeat request (HARQ) process ID, are transmitted from an eNBto higher layers of a recipient UE during a configuration stage prior tothe transmission of the data flow. A HARQ process is preferably assignedfor an entire data flow. Accordingly, the data flow ID and HARQ processID are preferably only transmitted once at the beginning of the dataflow and not on a per packet basis. For example, referring to FIG. 2, adata flow ID and HARQ process ID for a user equipment UE₁ is sent insub-frame 1 in connection with the assignment of frequency-time (FT)resources FT1 to UE₁. Similarly, a data flow ID and HARQ process ID foranother user equipment UE₂ is sent in sub-frame i in connection with theassignment of frequency-time (FT) resources FT1 to UE₂ following thecompletion of the use of FT1 by UE₁.

Additionally, packet sequence numbers are preferably assigned at higherradio link control (RLC) layers, such that sequence numbers are not usedat lower layers such as physical (PHY) and medium access control (MAC)layers. Accordingly, the reordering of packets that are received ishandled at or above the RLC layer, for example, by a layer 3 (L3)protocol such as radio resource control (RRC).

FIG. 4 is a flow diagram of a method 400 for high-level configuration ofRTS in accordance with the first embodiment of the present invention. Instep 405, an eNB sends a data flow ID (or equivalently a RAB or logicalchannel ID) and a HARQ process ID as part of a configuration message foran RTS data flow before the transmission of data flow packets, forexample in connection with FT1 assignment to UE₁ in subframe 1 of FIG.2. In step 410, the eNB does not include data flow ID and process IDfields in data flow packets for higher layers, but packet sequencenumbers are included in an RLC control header, for example, for packetstransmitted in subframes 2 though i−1 for the UE₁ communication of FIG.2 which ends. There is a resultant saving in higher layer signaling,since the higher layers received, for example, the data flow ID and HARQprocess ID for the communication regarding UE₁ in sub-frame 1 which arethen available for use in processing the data packets for the UE₁communication that are received in sub-frames 2 through i−1 withoutrepetitive signaling of the ID information. Further saving in signalingis realized through the elimination of sequence number signaling in thelower layers. In implementing method 400, a transmitter is configured totransmit data flow and HARQ process IDs in a configuration message andtransmit packet sequence numbers in an RLC control header.

According to a second embodiment of the present invention, a UEpreferably signals information to an eNB concerning variable data ratesin uplink (UL) communications. This is preferably done by reporting achange in data rate relative to a current data rate. An RTS data flow isinitially assigned a certain amount of physical resources in order tosupport a current data rate using, for example, persistent assignment.When the UE detects a new data rate, the UE preferably signals to theeNB the difference between the current data rate and the new data rate.By signaling only the difference in data rate, the number of overheadbits used is minimized.

By way of example, 4 reporting bits are required to report the actualdata rate when up to 9 codec rates as used in a VoIP service. Morereporting bits are used if more codec rates are available. When only thechange in data rate is reported, the number of reporting bits is reducedfrom 4 to 3 because the greatest change in data rate from the lowestrate to the highest rate is only 8. Preferably, the minimum number ofreporting bits is used to report the possible variations in data ratefor a particular RTS service.

The change in data rate of an RTS data flow over the UL may be signaledusing layer 1 (L1), layer 2 (L2) or layer 3 (L3) signaling, where L1includes the physical (PHY) layer, layer 2 includes the medium accesscontrol (MAC) and radio link control (RLC) layers and layer 3 includesthe radio resource control (RRC) layer. Alternatively, the change indata rate may be signaled at higher layers.

L1 signaling of changes in data rate of UL traffic is preferably doneusing L1 control signaling, such that variable data rate reporting bitsmay be multiplexed with other UL L1 signals including hybrid automaticrepeat request (HARQ), acknowledgment (ACK), negative acknowledgment(NAK) and channel quality indicator (CQI). Alternatively, an UL thinchannel may be used. The UL thin channel is preferably used by a UE thatneeds to report a rate change to the eNB in an expedited manner so thatthe eNB assigns new UL resources to the RTS sooner. In anotheralternative, a data rate change indication can be sent using asynchronous random access channel (RACH), where the RACH has the benefitof small access delays.

The signaling of changes in data rate of UL traffic at L2 is preferablydone by including rate change reporting bits in a MAC header of a packetscheduled for transmission over the UL. Alternatively, a rate changeindication can be piggybacked with any UL L2 packet if the timing of thepiggybacked packet is within a reasonable delay. Alternatively, a ratechange indication can be sent via MAC control packet data unit (PDU),where the MAC control PDU may exclusively contain the data rate changeindication or may contain other information for other control purposes.In another alternative, a rate change indication may be included in aperiodic RLC status report from the UE to the eNB. Using L3 signaling, achange in data rate may be signaled by including a rate changeindication in RRC signaling.

When the eNB detects the data rate change reported by a UE, the eNBdynamically reallocates physical resources assigned to the RTS of thatUE accordingly. For example, if the data rate decreased, then the eNBcan reallocate some of the resources originally assigned to the UEduring persistent assignment to other UEs. The eNB may assign additionalresources to the UE in the case of an increase in data rate.

Preferably, the dynamic allocation by the eNB overrides the initialresource allocation by persistent assignment. The eNB may specify a timeduration during which the dynamic allocation overrides the originalallocation when signaling the dynamic resource allocation to the UE. Ifno duration is specified, then it may be assumed that the dynamicallocation is only used once. The dynamic allocation by eNB to overridepersistent resource allocation is not only applicable to variable datarate services, but may also be used to reallocate resources forretransmissions.

FIG. 5 is a flow diagram of a method 500 for signaling variable datarates for UL RTS traffic, in accordance with the second embodiment ofthe present invention. A UE signals variable data rates for UL RTStraffic to an eNB by reporting the change in data rate relative to acurrent data rate using a minimum number of bits, in step 505. Thereporting may be done using L1, L2 or L3 signaling, as described above.In step 510, the eNB adjusts the amount of physical resources assignedto the UE for the RTS according to the reported change in data rate. Incontrast with the prior art of FIGS. 2 and 3, the FT resource allocationfor UE₁ made in sub-frame 1 does not necessarily remain fixed untilsub-frame i, but can be dynamically changed per step 510 in a sub-frameprior to sub-frame i. In implementing method 500, a transceivercomponent may be configured to transmit signals reflecting change indata rate, and a resource allocation component may be configured toallocate physical resources.

According to a third embodiment of the present invention, DL and ULradio resources assigned to an RTS data flow are dynamically allocatedin order to efficiently use the physical resources assigned to variabledata rates services. Typically, the maximum amount of radio resourcesrequired for an RTS are initially assigned by persistent allocation, inorder to support the maximum data rate for the RTS. For illustrativepurposes, it is assumed that a set of N radio blocks are initiallyallocated by persistent scheduling. The eNB preferably dynamicallyallocates only a subset of the N radio blocks to the RTS data low whenlower data rates are required. Under higher data rates, the eNBallocates a larger set of radio blocks, and can allocate new radioblocks in addition to the original set of N radio blocks, if desired. Ifsub-band allocation is supported, where radio resources are allocatedaccording to fractions of a radio block, then dynamic resourceallocation is preferably adapted to the granularity of sub-bands.

Preferably, only the change in radio resource allocation resulting fromdynamic resource allocation is signaled by the eNB to the target UE inorder to reduce signaling overhead. In one embodiment, the radioresource blocks assigned to the RTS are indexed, such that the radioblocks may be arranged in increasing or decreasing order according toindex number. Accordingly, the eNB only signals the number of radioblocks for dynamic allocation, such that the UE accordingly uses thereported number of radio blocks in order of index number starting withthe radio block with either lowest or the highest index number. By wayof example, radio blocks indexed 2, 3, 5 and 8 are assigned to a UE(i.e. N=4) for an RTS data flow during persistent scheduling. Inresponse to a decrease in data rate, the eNB reports that only 3 radioblocks are dynamically allocated to the UE. Based on the report from theeNB and starting with the lowest index, the UE knows that the newresource allocation is radio blocks 2, 3 and 5. Alternatively, apositive or negative difference between the original allocation of Nblocks and the number needed may be signaled. Where more blocks arerequired, default parameters can be provided or block identification canbe signaled for the additional blocks.

A new radio resource allocation is preferably signaled by a eNB to a UEas a field in L1 or L2 control signaling for fast DL or UL dynamicresource allocation, or, in L3 RRC signaling in the case of slowlychanging resource allocation. When L1 or L2 control signaling is used, aphysical layer ACK or NAK is preferably transmitted back to the eNB toimprove the reliability of the resource allocation signaling.Additionally, information including, but not limited to, the duration ofnew radio resource allocation, repetition period, sequence pattern,radio resource and the frequency hopping pattern may be provided as partof the radio resource allocation signaling, when desired.

FIG. 6 is a flow diagram of a method 600 for dynamic allocation andsignaling of radio resources at an eNB for RTS with variable data rates,in accordance with the third embodiment of the present invention. Instep 605, an eNB is notified of a change in data rate for an RTS dataflow over a wireless link between the eNB and a UE such that N radioblocks are currently assigned to the RTS. In step 610, the eNBdynamically allocates radio blocks to the UE for the RTS data flow inresponse to the change in data rate such that if the data ratedecreased, then a subset of the N radio blocks are assigned, and if thedata rate increased, then additional radio blocks are assigned. In step615, the eNB signals to the UE the new radio block allocation by onlysignaling the change in radio block assignment. In contrast with theprior art of FIGS. 2 and 3, the FT resource allocation for UE, made insub-frame 1 does not necessarily remain fixed until sub-frame i, but canbe dynamically changed per step 615 prior to sub-frame i. Inimplementing method 600, a data rate detection component may beconfigured to detect changes in data rate associated with a data flow,and a resource allocation component can be configured to allocatephysical resources and is associated with a transmitter in order tosignal resource allocations to a UE.

In accordance with a fourth embodiment of the present invention, a tablerelating data rates to radio resource characteristics is used forefficient radio resource allocation and signaling of UL resources. Boththe eNB and the UE preferably store a pre-calculated table relating anumber of radio resource blocks, or when applicable sub-bands, requiredfor RTS data rates for a range of channel conditions according to, forexample, modulation and coding scheme (MCS). When a new data rate isidentified at the UE for a current RTS data flow over the UL, the UEpreferably calculates the needed radio resources under determined ULchannel conditions based on the table entry for that data rate.Accordingly, the UE does not have to communicate with the eNB to adaptits resource assignment, and overhead control signaling to the eNB isreduced.

In a preferred embodiment, the eNB signals a pre-allocated table to theUE where the table identifies specific radio resources, such as radioblocks or sub-bands, that are required for various RTS data rates for arange of channel conditions. For example, radio blocks may be referredto by index number, as described above. The UE dynamically allocates ULresources in response to a change in data rate of an RTS data flow bylooking up the corresponding resources in the table, and signals theassigned resource set to the eNB. The UE may wait for an approvalmessage from the eNB before using the newly assigned UL resources. TheeNB preferably sends an approval of new radio resource assignment whenadditional resources are allocated to accommodate an increase in datarate. The approval message from the eNB is optional when radio resourcesare deallocated for decreases in data rate.

FIG. 7 is a flow diagram of a method 700 for dynamic allocation andsignaling of radio resources at a user equipment (UE) for RTS withvariable data rates, in accordance with the fourth embodiment of thepresent invention. In step 705, a UE receives a table from an eNB thatmaps required radio resources or resource characteristics to RTS datarates under predetermined channel conditions. In step 710, the UEdetects a change in data rate of an UL RTS data flow, and determines thecorresponding radio resource allocation from the table. In step 715, theUE signals the determined radio resource allocation to the eNB and waitsfor an approval signal from the eNB before using the determined radioresources. In contrast with the prior art of FIGS. 2 and 3, the FTresource allocation for UE₁ made in sub-frame 1 does not necessarilyremain fixed until sub-frame i, but can be dynamically changed in asub-frame prior to sub-frame i. In implementing method 700, atransceiver is used to receive the table from the eNB and signal radioresource allocations to the eNB, and a data rate detection component isconfigured to detect changes in data rate.

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the preferred embodiments or in various combinations with orwithout other features and elements of the present invention. Themethods or flow charts provided in the present invention may beimplemented in a computer program, software, or firmware tangiblyembodied in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any integrated circuit,and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for in use in a wireless transmit receiveunit (WTRU), user equipment, terminal, base station, radio networkcontroller, or any host computer. The WTRU may be used in conjunctionwith modules, implemented in hardware and/or software, such as a camera,a video camera module, a videophone, a speakerphone, a vibration device,a speaker, a microphone, a television transceiver, a hands free headset,a keyboard, a Bluetooth® module, a frequency modulated (FM) radio unit,a liquid crystal display (LCD) display unit, an organic light-emittingdiode (OLED) display unit, a digital music player, a media player, avideo game player module, an Internet browser, and/or any wireless localarea network (WLAN) module.

What is claimed:
 1. A wireless transmit/receive unit (WTRU) comprising:a receiver configured to receive first control information indicating afirst allocation of resources, wherein the first allocation of resourcesindicates at least a first number of resource blocks assigned to theWTRU and is associated with a first data rate; a transmitter configuredto transmit first uplink data according to the first allocation ofresources; while the first allocation of resources is valid: thereceiver configured to receive second control information indicating asecond allocation of resources, wherein the second allocation ofresources indicates at least a second number of resource blocks assignedto the WTRU and is associated with a second data rate different than thefirst data rate; and the transmitter configured to transmit seconduplink data according to the second allocation of resources instead ofthe first allocation of resources for a predetermined time duration,wherein the predetermined time duration is not specified by the secondcontrol information.
 2. The WTRU of claim 1, wherein the transmitter isfurther configured to transmit third uplink data according to the firstallocation of resources after the predetermined time duration withoutreceiving additional signaling.
 3. The WTRU of claim 1, wherein thesecond allocation of resources overrides the first allocation ofresources during the predetermined time duration.
 4. The WTRU of claim1, wherein the first and second control information is received as L1/L2control information in an orthogonal frequency division multiple access(OFDMA) format.
 5. The WTRU of claim 4, wherein the first allocation ofresources and the second allocation of resources are distinguished bydifferent identifications (IDs).
 6. The WTRU of claim 1, wherein thepredetermined time duration is a single subframe.
 7. The WTRU of claim6, wherein the transmitter is further configured to transmit thirduplink data according to the first allocation of resources after thesingle subframe in a next subframe adjacent to the single subframe. 8.The WTRU of claim 1, wherein the transmitter is further configured totransmit retransmissions of uplink data according to the secondallocation of resources for the predetermined time duration.
 9. The WTRUof claim 1, wherein the first number of resource blocks indicates afirst number of subchannels assigned to the WTRU and the second numberof resource blocks indicates a second number of subchannels assigned tothe WTRU.
 10. The WTRU of claim 1, wherein the transmitter is furtherconfigured to utilize the first allocation of resources for transmittinguplink data until the WTRU receives a deallocation of the firstallocation of resources.
 11. The WTRU of claim 1, wherein the firstallocation of resources is valid after the predetermined time duration.12. A wireless transmit/receive unit (WTRU) comprising: a receiverconfigured to receive first control information indicating a firstallocation of resources, wherein the first allocation of resourcesindicates at least a first number of resource blocks assigned to theWTRU and is associated with a first data rate; the receiver configuredto receive first downlink data according to the first allocation ofresources; while the first allocation of resources is valid: thereceiver configured to receive second control information indicating asecond allocation of resources, wherein the second allocation ofresources indicates at least a second number of resource blocks assignedto the WTRU and is associated with a second data rate different than thefirst data rate; and the receiver configured to receive second downlinkdata according to the second allocation of resources instead of thefirst allocation of resources for a predetermined time duration, whereinthe predetermined time duration is not specified by the second controlinformation.
 13. The WTRU of claim 12, wherein the receiver is furtherconfigured to receive third downlink data according to the firstallocation of resources after the predetermined time duration withoutreceiving additional signaling.
 14. The WTRU of claim 12, wherein thesecond allocation of resources overrides the first allocation ofresources during the predetermined time duration.
 15. The WTRU of claim12, wherein the first and second control information is received asL1/L2 control information in an orthogonal frequency division multipleaccess (OFDMA) format.
 16. The WTRU of claim 15, wherein the firstallocation of resources and the second allocation of resources aredistinguished by different identifications (IDs).
 17. The WTRU of claim12, wherein the predetermined time duration is a single subframe. 18.The WTRU of claim 17, wherein the receiver is further configured toreceive third downlink data according to the first allocation ofresources after the single subframe in a next subframe adjacent to thesingle subframe.
 19. The WTRU of claim 12, wherein the receiver isfurther configured to receive retransmissions of downlink data accordingto the second allocation of resources for the predetermined timeduration.
 20. The WTRU of claim 12, wherein the first number of resourceblocks indicates a first number of subchannels assigned to the WTRU andthe second number of resource blocks indicates a second number ofsubchannels assigned to the WTRU.
 21. The WTRU of claim 12, wherein thereceiver is further configured to utilize the first allocation ofresources for receiving downlink data until the WTRU receives adeallocation of the first allocation of resources.
 22. The WTRU of claim12, wherein the first allocation of resources is valid after thepredetermined time duration.
 23. A base station comprising: atransmitter configured to transmit, to a wireless transmit/receive unit(WTRU), a first control information indicating a first allocation ofresources, wherein the first allocation of resources indicates at leasta first number of resource blocks assigned to the WTRU and is associatedwith a first data rate; a receiver configured to receive, from the WTRU,first uplink data according to the first allocation of resources; whilethe first allocation of resources is valid: the transmitter configuredto transmit, to the WTRU, second control information indicating a secondallocation of resources, wherein the second allocation of resourcesindicates at least a second number of resource blocks assigned to theWTRU and is associated with a second data rate different than the firstdata rate; and the receiver configured to receive, from the WTRU, seconduplink data according to the second allocation of resources for apredetermined time duration, wherein the predetermined time duration isnot specified by the control information.
 24. A base station comprising:a transmitter configured to transmit, to a wireless transmit/receiveunit (WTRU), first control information indicating a first allocation ofresources, wherein the first allocation of resources indicates at leasta first number of resource blocks assigned to the WTRU and is associatedwith a first data rate; the transmitter configured to transmit, to theWTRU, first downlink data according to the first allocation ofresources; while the first allocation of resources is valid: thetransmitter configured to transmit, to the WTRU, second controlinformation indicating a second allocation of resources, wherein thesecond allocation of resources indicates at least a second number ofresource blocks assigned to the WTRU and is associated with a seconddata rate different than the first data rate; and the transmitterconfigured to transmit, to the WTRU, second downlink data according tothe second allocation of resources instead of the first allocation ofresources for a predetermined time duration, wherein the predeterminedtime duration is not specified by the control information.
 25. A methodperformed by a wireless transmit/receive unit (WTRU), the methodcomprising: receiving first control information indicating a firstallocation of resources, wherein the first allocation of resourcesindicates at least a first number of resource blocks assigned to theWTRU and is associated with a first data rate; transmitting first uplinkdata according to the first allocation of resources; while the firstallocation of resources is valid: receiving second control informationindicating a second allocation of resources, wherein the secondallocation of resources indicates at least a second number of resourceblocks assigned to the WTRU and is associated with a second data ratedifferent than the first data rate; and transmitting second uplink dataaccording to the second allocation of resources instead of the firstallocation of resources for a predetermined time duration, wherein thepredetermined time duration is not specified by the second controlinformation.
 26. The method of claim 25, further comprising:transmitting third uplink data according to the first allocation ofresources after the predetermined time duration without receivingadditional signaling.
 27. The method of claim 25, wherein the secondallocation of resources overrides the first allocation of resourcesduring the predetermined time duration.
 28. The method of claim 25,wherein the first and second control information is received as L1/L2control information in an orthogonal frequency division multiple access(OFDMA) format.
 29. The method of claim 28, wherein the first allocationof resources and the second allocation of resources are distinguished bydifferent identifications (IDs).
 30. The method of claim 25, wherein thepredetermined time duration is a single subframe.
 31. The method ofclaim 30, further comprising: transmitting third uplink data accordingto the first allocation of resources after the single subframe in a nextsubframe adjacent to the single subframe.
 32. The method of claim 25,further comprising: transmitting retransmissions of uplink dataaccording to the second allocation of resources for the predeterminedtime duration.
 33. The method of claim 25, wherein the first number ofresource blocks indicates a first number of subchannels assigned to theWTRU and the second number of resource blocks indicates a second numberof subchannels assigned to the WTRU.
 34. The method of claim 25, whereinthe first allocation of resources is utilized for transmitting uplinkdata until the WTRU receives a deallocation of the first allocation ofresources.
 35. The method of claim 25, wherein the first allocation ofresources is valid after the predetermined time duration.
 36. A methodperformed by a wireless transmit/receive unit (WTRU), the methodcomprising: receiving first control information indicating a firstallocation of resources, wherein the first allocation of resourcesindicates at least a first number of resource blocks assigned to theWTRU and is associated with a first data rate; receiving first downlinkdata according to the first allocation of resources; while the firstallocation of resources is valid: receiving second control informationindicating a second allocation of resources, wherein the secondallocation of resources indicates at least a second number of resourceblocks assigned to the WTRU and is associated with a second data ratedifferent than the first data rate; and receiving second downlink dataaccording to the second allocation of resources instead of the firstallocation of resources for a predetermined time duration, wherein thepredetermined time duration is not specified by the second controlinformation.
 37. The method of claim 36, further comprising: receivingthird downlink data according to the first allocation of resources afterthe predetermined time duration without receiving additional signaling.38. The method of claim 36, wherein the second allocation of resourcesoverrides the first allocation of resources during the predeterminedtime duration.
 39. The method of claim 36, wherein the first and secondcontrol information is received as L1/L2 control information in anorthogonal frequency division multiple access (OFDMA) format.
 40. Themethod of claim 39, wherein the first allocation of resources and thesecond allocation of resources are distinguished by differentidentifications (IDs).
 41. The method of claim 36, wherein thepredetermined time duration is a single subframe.
 42. The method ofclaim 41, further comprising: receiving third downlink data according tothe first allocation of resources after the single subframe in a nextsubframe adjacent to the single subframe.
 43. The method of claim 36,further comprising: receiving retransmissions of downlink data accordingto the second allocation of resources for the predetermined timeduration.
 44. The method of claim 36, wherein the first number ofresource blocks indicates a first number of subchannels assigned to theWTRU and the second number of resource blocks indicates a second numberof subchannels assigned to the WTRU.
 45. The method of claim 36, whereinthe first allocation of resources is utilized for receiving downlinkdata until the WTRU receives a deallocation of the first allocation ofresources.
 46. The method of claim 36, wherein the first allocation ofresources is valid after the predetermined time duration.
 47. A methodperformed by a base station, the method comprising: transmitting, to awireless transmit/receive unit (WTRU), a first control informationindicating a first allocation of resources, wherein the first allocationof resources indicates at least a first number of resource blocksassigned to the WTRU and is associated with a first data rate;receiving, from the WTRU, first uplink data according to the firstallocation of resources; while the first allocation of resources isvalid: transmitting, to the WTRU, second control information indicatinga second allocation of resources, wherein the second allocation ofresources indicates at least a second number of resource blocks assignedto the WTRU and is associated with a second data rate different than thefirst data rate; and receiving, from the WTRU, second uplink dataaccording to the second allocation of resources for a predetermined timeduration, wherein the predetermined time duration is not specified bythe control information.
 48. A method performed by a base station, themethod comprising: transmitting, to a wireless transmit/receive unit(WTRU), first control information indicating a first allocation ofresources, wherein the first allocation of resources indicates at leasta first number of resource blocks assigned to the WTRU and is associatedwith a first data rate; transmitting, to the WTRU, first downlink dataaccording to the first allocation of resources; while the firstallocation of resources is valid: transmitting, to the WTRU, secondcontrol information indicating a second allocation of resources, whereinthe second allocation of resources indicates at least a second number ofresource blocks assigned to the WTRU and is associated with a seconddata rate different than the first data rate; and transmitting, to theWTRU, second downlink data according to the second allocation ofresources instead of the first allocation of resources for apredetermined time duration, wherein the predetermined time duration isnot specified by the control information.